1. Field of the Invention
This invention concerns biscationic, disazo dyes for dyeing acid-modified nylon styling yarns under neutral to weakly acidic conditions.
2. Description of the Prior Art
With the introduction of acid-modified nylons the range of multicolored effects obtainable on bulk continuous filament BCF nylon styling carpeting has been increased. Acid-modified nylons, which contain sulfonic acid groups on the polymer chain, are dyeable with cationic dyes but have little or no affinity for acid dyes. Thus, a carpet containing two or three nylons of varying affinity for acid dyes (nonacid-modified nylons) and an acid-modified nylon that is not stained by acid dyes can be dyed at will with any combination of shades, including primary colors (those colors that cannot be obtained by combining other colors) side by side on the same carpet. Dyeing methods have been developed so that such carpets can be dyed with acid and cationic dyes in a single dyeing operation.
The following are among the most important considerations when choosing cationic dyes for the acid-modified nylon fibers in nylon styling carpeting and these considerations are met by the novel dyes of this invention:
1. the dyes should have a high degree of light-fastness;
2. they should show a minimum of cross-staining on the unmodified nylon yarns; cross-staining causes dullness, a decrease in shade contrast between yarns of different colors and possibly a decrease in fastness properties;
3. they should have a high degree of a wetfastness, to prevent cross-staining of the unmodified nylon yarns when the carpet is shampooed.